unobtainably en · ADV
Etymology
From unobtainable + -ly.
Meanings
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Such that it cannot be obtained.
Second, the efficiency of an absorption machine increases with decreased generator pressure, but this is limited in practical work because a low generator pressure calls for cooling water of unobtainably low temperature.
1921, Charles L. Hubbard, “Refrigeration”, in American Architect and Architecture, volume 119, page 587:They just seem more Romantic, more alluring, stronger and of course more unobtainably desirable when they stay alone.
1998, Diane Wakoski, Argonaut Rose: